Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.


  1. Advanced Patent Search
Publication numberUS5189543 A
Publication typeGrant
Application numberUS 07/615,567
Publication dateFeb 23, 1993
Filing dateNov 19, 1990
Priority dateNov 19, 1990
Fee statusPaid
Publication number07615567, 615567, US 5189543 A, US 5189543A, US-A-5189543, US5189543 A, US5189543A
InventorsSteve Lin, Kent Kao, Robert Hsue
Original AssigneeAcer Incorporated
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Infra-red wireless keyboard system
US 5189543 A
A communication system comprising a wireless keyboard for emitting infra-red signals, a receiving unit for converting the infra-red signals to an electrical signal, a tuning and amplifying circuit coupled to the receiving unit for tuning and amplifying the electrical signals, a carrier filtering circuit for removing the carrier component of the input signal, a single-shot circuit coupled to the carrier filtering circuit for converting its input signal to a known code wave form, and a microprocessor for receiving the code wave. The invention allows multiple users to operate their wireless keyboards without interference.
Previous page
Next page
What is claimed is:
1. A communication system comprising:
a wireless keyboard means for emitting infra-red signals, the infra-red signals comprising an ID code and data, the code and data being transmitted according to a predefined communication format at a user-selected carrier frequency, the wireless keyboard means including a channel switch circuit for user selection of the carrier frequency;
a receiving means for receiving the infra-red signals and for converting the received signals to an electrical signal;
a tuning and amplifying circuit means coupled to the receiving means, the tuning circuit capable of being tuned to a preset carrier frequency by the user, the tuning circuit receiving the electrical signal and transmitting it to the amplifying circuit if the carrier frequency of the electrical signal and the preset carrier frequency tuned on the tuning circuit means are the same, the amplifying circuit amplifying the electrical signal;
a carrier filtering circuit means, coupled to the tuning and amplifying circuit means for filtering the carrier component of the electrical signal;
single-shot circuit means coupled to the carrier filtering circuit means, the single-shot circuit means converting the demodulated electrical signal to a code wave signal compatible with a predefined communication signal protocol; and
a microprocessor coupled to the single-shot circuit means for receiving said code wave signal and for determining if the ID code is correct.
2. The system of claim 1, wherein the tuning and amplifying circuit comprises a remote control preamplifier and at least one tuning circuit for allowing a user to select among a plurality of frequencies.
3. The system of claim 1, wherein said predefined communications format is the RS 232 signal protocol.

This invention is in the field of infra-red communications. More particularly, it relates to multi-user infra-red communication systems.

Methods and apparatus for emitting infra-red signals for use in wireless communication systems are known. One such system is shown in U.S. Pat. No. 4,628,541, the specification of which is incorporated herein for all purposes. Known infra-red wireless keyboard systems can accommodate multiple users with multiple channels. In operation, an ID code is combined with the signals transmitted by the wireless keyboard. This combined signal is then transmitted at a particular carrier frequency. The receiver, which is coupled to the computer system, can determine from the received ID code which channel the keyboard is using. Although this arrangement allows for multiple users, these multiple users cannot simultaneously access the computer without causing mutual interference. If two users were to attempt to input data simultaneously into their respective computer systems, the fact that the carrier frequencies are the same will result in the loss of the ID code and data to both systems.

As an example of the interference problem, assume two different users are transmitting to two separate computer systems, the first user transmitting on channel 1 and the second user transmitting on channel 2. Using known wireless keyboard systems, the first user can transmit data to the first computer system through channel 1, but if the second user attempts to transmit data simultaneously to the second system, both sets of data will be destroyed due to interference.

Given the limitations of the known wireless keyboard systems, a wireless keyboard that can transmit data simultaneously with other keyboards without interfering with them or being interfered with would be an advance of the known art.


In a preferred embodiment of the present invention, each channel is programmed with its own ID code and its own designated carrier frequency. Whenever a key is depressed, the key code and the ID code are transmitted according to the known RS 232 format at a designated frequency by an infra-red Light Emitting Diode (`LED`). The receiving unit receives the infra-red signal and outputs a corresponding electrical signal to a tuning and amplifying circuit for further processing. The processed signals are transmitted to a carrier filtering circuit which strips off the carrier and outputs the result to a single-shot circuit. The single-shot circuit converts the signals to a code wave of RS 232 type which is then sent to the microprocessor.

The carrier frequency is designated by the user, within a narrow band of frequencies. The ID codes and the carrier frequency associated with each channel is different. Thus, even if multiple users are transmitting simultaneously, the tuning circuit of the receiver can be set to a particular carrier frequency, rejecting simultaneously received signals having different carrier frequencies.

The invention will now be described in detail with reference to the figures listed and described below.


FIG. 1 is a block diagram of an infra-red wireless keyboard which incorporates the present invention;

FIG. 2 is a block diagram of a receiver for receiving signals from the wireless keyboard, the receiver incorporating the present invention; and

FIG. 3 is a detailed circuit diagram of the tuning, amplifying and carrier-filtering circuits shown in FIG. 2.


FIG. 1 is a block diagram of an infra-red wireless keyboard/transmitter constructed according to the teaching of the present invention. It comprises microprocessor 1, key matrix 2, channel switch 3, infra-red driver 4, power source control circuit 5 and battery 6. Channel switch 3 allows a user to select and operate on a given channel with a carrier frequency preassigned by microprocessor 1.

In operation, microprocessor 1 sends scanning signals to key matrix 2 in order to detect the depression of one of the keys. If no keys are depressed, power source control circuit 5 places microprocessor 1 into a low-power standby mode. Control circuit 5 also resets microprocessor 1 if power is cut off, ensuring proper microprocessor operation in all cases. If a key has been depressed, control circuit 5 switches microprocessor 1 to a normal operating mode. Microprocessor 1 assigns a key code to the depressed key according to its position in the key matrix. Microprocessor 1 then references channel switch 3 to obtain the proper ID code, each channel having a predefined ID code. The ID code and the key code are then combined into a 2 byte data word by microprocessor 1. Software in microprocessor 1 then generates a carrier frequency preassigned to the selected channel by microprocessor 1. Microprocessor 1 transmits the 2 byte data word according to a known communications format such as RS 232, at the carrier frequency. Infra-red driver 4 emits the data through an infra-red LED.

FIG. 2 shows a receiver of infra-red signals constructed according to the teachings of the present invention. It comprises receiving unit 20, tuning and amplifying circuit 21, carrier filtering circuit 22, single-shot circuit 23, and microprocessor 24.

Receiving unit 20 receives infra-red signals from infra-red driver 4 and outputs a corresponding electrical signal to tuning and amplifying circuit 21. If the carrier frequency of the received signal does not match the user-preset frequency designated by the tuning circuit, the received signal is rejected. If the carrier frequency of the received signal matches the preset frequency designated by the tuning circuit 21, the received signal is amplified by the amplifying circuit 21. The amplified signal is then sent to carrier filtering circuit 22 which strips off the carrier and sends the resulting signal to single-shot circuit 23. Single-shot circuit 23 converts its input into a code wave signal having a wave form of RS 232 type and sends this RS 232 wave to microprocessor 24. The width of the code wave pulse is controlled by the time constant control signals, generated by control circuit 26. Microprocessor 24 receives the ID code and data code outputted by single-shot circuit 23. If the ID code is correct, the data code will be received and sent to a computer system (not shown in FIG. 2) via keyboard connector 25. It should be noted that interference problems could occur with the present invention, if several users in the same area attempt to tune their transmitters and receivers to the same frequency. In this case, some procedure must be implemented to allocate the frequencies.

FIG. 3 shows the tuning and amplifying circuit 21 and carrier filter circuit 22 of FIG. 2 in greater detail. The functions of circuits 21 and 22 are performed by a NEC μPC 1474HA integrated circuit and two discrete tuning circuits. The output is provided on pin 1 of the integrated circuit, which is the output of carrier filtering circuit 22 in FIG. 2. The detailed description of the UPC 1474 HA is contained in a product specification appended hereto as Appendix A.

The present invention has now been described in a preferred embodiment. Various changes and modifications are readily envisioned and fully within the scope of the invention. For example other communications means other than an RS 232 communications means can be used. Additionally, the tuning and amplifying circuit of FIG. 2 could be duplicated in order to have a more accurate band pass function. Accordingly, the scope of the invention should be limited only by the breadth of the claims.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US4628541 *Feb 15, 1985Dec 9, 1986International Business Machines CorporationInfra-red data communications system for coupling a battery powered data entry device to a microcomputer
US4897821 *Jan 27, 1989Jan 30, 1990Institut Francais Du PetroleMethod and device for initializing data, and particularly seismic data, acquisition apparatus
US4905279 *Dec 1, 1988Feb 27, 1990Nec Home Electronics Ltd.Learning-functionalized remote control receiver
US4914517 *Apr 6, 1989Apr 3, 1990Thomson Consumer Electronics, Inc.Tuner control apparatus having tune-by-label capability and using alphabetical label storage
Non-Patent Citations
1 *Infoworld, Jul. 17, 1989, Darrow, B. (359/172).
2 *Photolink RS 232, Photonics Corporation 1989. (359/172).
3Photolink™ RS-232, Photonics Corporation 1989. (359/172).
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5394259 *Feb 24, 1993Feb 28, 1995Sony CorporationModulation/demodulation apparatus and information processing apparatus
US5406273 *Jul 25, 1994Apr 11, 1995Sharp Kabushiki KaishaData processor
US5504606 *Jun 1, 1994Apr 2, 1996At&T Corp.Low power optical network unit
US5515051 *Mar 5, 1993May 7, 1996Sharp Kabushiki KaishaWireless signaling system
US5557751 *Jul 12, 1995Sep 17, 1996Sun Microsystems, Inc.Method and apparatus for serial data communications using FIFO buffers
US5574585 *Jun 28, 1995Nov 12, 1996Feller AgTransmission method and apparatus for an infrared remote control system
US5602669 *Jun 26, 1995Feb 11, 1997Sony CorporationDigital signal transmission apparatus, digital signal transmission method, and digital signal transmitter-receiver
US5734328 *Dec 14, 1994Mar 31, 1998Canon Kabushiki KaishaApparatus for switching communication method based on detected communication distance
US5757354 *Oct 24, 1995May 26, 1998Sony CorporationPortable data communication apparatus with rotatable display images for accomodating a wireless remote keyboard
US5861822 *Sep 2, 1997Jan 19, 1999Samsung-Electro Mechanics Co., Ltd.Wire/wireless keyboard, and control method therefor
US5870033 *Nov 10, 1994Feb 9, 1999Strolo; LotharKeyboard, in particular a membrane keyboard
US5903259 *Mar 31, 1997May 11, 1999Compaq Computer CorporationMethod and apparatus for mapping remote control buttons onto keyboard stroke combinations
US5925110 *Aug 22, 1997Jul 20, 1999Micron Electronics, Inc.Low power keyboard with power supply switch that is activated by receiver output to power up and down keyboard components including microcontroller demodulator
US5929777 *May 16, 1996Jul 27, 1999Mci World Com, Inc.Radio activated personal infrared distress beacon
US5955975 *Sep 30, 1997Sep 21, 1999Compaq Computer CorporationApparatus and associated method for recovering lost break codes for wireless keyboards
US5958023 *Jan 7, 1997Sep 28, 1999Micron Electronics, Inc.Method for low power wireless keyboard that detects a host computer query for the state of a key then powers up to determine and transmit back the state of that key
US6028538 *Oct 10, 1997Feb 22, 2000Ericsson Inc.Method, keyboard and system for transmitting key characters
US6031470 *Jan 9, 1998Feb 29, 2000Sony CorporationMethod and device for transmitting key operation information and transmission-reception system
US6046731 *May 8, 1997Apr 4, 2000Ericsson Inc.Method and apparatus for split keyboard control
US6088143 *Jan 23, 1998Jul 11, 2000Samsung Electronics Co., Ltd.Remote infrared password key system and methods for controlling the same
US6195712 *Jun 13, 1997Feb 27, 2001Intel CorporationDynamic discovery of wireless peripherals
US6211862 *Mar 13, 1998Apr 3, 2001Samsung Electronics Co., Ltd.Wire/wireless keyboard for use in a computer system and a method of operating the same
US6229526 *Dec 18, 1997May 8, 2001International Business Machines CorporationMethod and system for simultaneous operation of multiple handheld IR control devices in a data processing system
US6304250Apr 13, 1998Oct 16, 2001Samsung Electronics Co., Ltd.Wire/wireless keyboard with pointing device attachable thereto, computer system for use with the same, and related method
US6359610Apr 28, 1998Mar 19, 2002Pragmatic Communications Systems, Inc.Wireless interface system for allowing a plurality of input devices to control a processor
US6571299 *Jan 25, 1999May 27, 2003Robert SchroyerSystem for receiving ID-codes from at least one wireless transmitter having a plurality of transmitter buttons each of them being individually programmed
US6573843Jul 14, 1999Jun 3, 2003Micron Technology, Inc.Snap-on keyboard and method of integrating keyboard
US6650254 *Mar 13, 2000Nov 18, 2003ErgodexComputer input device with individually positionable and programmable switches
US6664949Nov 5, 1999Dec 16, 2003International Business Machines CorporationInteroperable/heterogeneous environment keyboard
US6686671 *Sep 25, 2000Feb 3, 2004Matsushita Electric Industrial Co., Ltd.Key input circuit, power supply control apparatus, and power supply control method
US6888898 *May 25, 2000May 3, 2005Logitech Europe S.A.Random code for device identification
US7020785 *Feb 8, 2001Mar 28, 2006Samsung Electronics, Co., Ltd.Method for automatically verifying security code of computer system operated by remote controller
US7054361May 31, 2000May 30, 2006Thomson LicensingMethod and apparatus for enhancing an infrared signal protocol
US7158055Oct 17, 2003Jan 2, 2007Matsushita Electric Industrial Co., Ltd.Key input circuit, power supply control apparatus, and power supply control method
US7227530 *Jul 28, 2000Jun 5, 2007Tai-Her YangAssembly of independent mouse or track ball device using keyboard as an operational relay with keyboard
US7352862 *Jun 20, 2002Apr 1, 2008Nagano Fujitsu Component LimitedEncryption method, communication system, transmission device, and data input device
US7500022 *Jun 28, 2005Mar 3, 2009Mirco-Star Int'l Co., Ltd.Computer system with built-in multimedia system where multimedia system is operable independent of the operating system of the computer system and where computer system is capable of outputting video
US20010020276 *Feb 8, 2001Sep 6, 2001Hong-Sam KimMethod for automatically verifying security code of computer system operated by remote controller
US20030039356 *Jun 20, 2002Feb 27, 2003Nagano Fujitsu Component LimitedEncryption method, communication system, transmission device, and data input device
US20040084969 *Oct 17, 2003May 6, 2004Matsushita Electric Industrial Co., Ltd.Key input circuit, power supply control apparatus, and power supply control method
US20050035950 *Sep 23, 2004Feb 17, 2005Ted DanielsPortable input device for computer
US20050228909 *Mar 30, 2005Oct 13, 2005Micro-Star International Co., Ltd.Computer system capable of audio and video playback while in a non-booted state
US20060294268 *Jun 28, 2005Dec 28, 2006Chun-Chang YangComputer system capable of outputting video signals to an external display device
US20080018518 *Jul 19, 2007Jan 24, 2008Asustek Computer Inc.Remote system capable of controlling an electronic device and method thereof
US20090292992 *Jul 30, 2009Nov 26, 2009Micro-Star International Co., Ltdcomputer system and a switching method for the same
CN1114854C *Apr 12, 1998Jul 16, 2003三星电子株式会社Computer system using wire/wireless keyboard with attachable pointing device
EP0867798A2 *Mar 9, 1998Sep 30, 1998International Business Machines CorporationData processing system user interface
EP0867798A3 *Mar 9, 1998Apr 19, 2006International Business Machines CorporationData processing system user interface
WO1999019790A1 *Oct 2, 1998Apr 22, 1999Ericsson Inc.Method, keyboard, and system for transmitting key characters
U.S. Classification398/106, 398/130
International ClassificationH04B10/10
Cooperative ClassificationH04B10/114
European ClassificationH04B10/114
Legal Events
Jan 22, 1991ASAssignment
Owner name: ACER INC.
Effective date: 19910107
Mar 18, 1994ASAssignment
Effective date: 19940301
Apr 1, 1996FPAYFee payment
Year of fee payment: 4
Aug 22, 2000FPAYFee payment
Year of fee payment: 8
Oct 17, 2003ASAssignment
Effective date: 20011231
Aug 23, 2004FPAYFee payment
Year of fee payment: 12